1. Field of the Invention
The invention concerns a compressor system for an internal combustion engine of the type described in the precharacterizing portion of claim 1, that is, a turbocharger system having at least two stages, wherein each of the stages of the compressor system respectively includes a turbine and a compressor, which are coupled to each other via a common shaft. The invention further concerns an internal combustion engine with a compressor system.
2. Description of the Related Art
One example of such compressor system is an exhaust gas driven turbocharger. Modern turbocharged internal combustion engines are equipped with a two-stage turbocharger. A two-stage turbocharger includes a low-pressure stage as well as a high-pressure stage, which respectively include a compressor and a turbine. Turbine and compressor are connected to each via a common shaft. A generic internal combustion engine with such a two-stage compressor system is described for example in German OS DE 198 37 978 A1 and DE 195 14 572 A1 in such detail that their construction and manner of operation need not be described herein in greater detail.
A problem with a two or more stage turbocharger is the space necessary therefore, in view of the limited space available in the engine compartment. This problem is particularly serious in commercial vehicles, in which the individual turbocharger stages must naturally be dimensioned much larger than in the case of personal vehicles and therewith require a substantial amount of space in the engine compartment. This is however often not available, so that the space requirement for a two-stage turbocharger often leads to insolvable problems.
An arrangement is described in German patent application DE 198 22 874 A1 in which two exhaust gas turbochargers are integrated in a common housing. The arrangement described in DE 198 22 874 A1 however concerns a manner of integration of two turbochargers arranged in parallel on the exhaust gas side, each of which respectively exhibiting a single turbocharger stage. The two parallel turbochargers exhibit a common inlet and two separate exhaust gas outlets. The particular advantage of the arrangement described in DE 198 22 874 A1 is comprised therein, that the otherwise conventional separate manifold can be dispensed with.
The integration to two turbochargers into a single housing described in German OS DE 198 22 874 A1 could however not be adapted easily to a two-stage turbocharger. The reason therefore is that a parallel arrangement of turbochargers exhibits basically a different construction of the housing than in the case of a series arrangement. In particular, one could point out that in a parallel arrangement in simple manner by the simple combining of the inlets and/or outlets (as in DE 198 22 874 A1) a space saving can be achieved by saving piping. This measure can however not easily be applied to a sequential design of a turbocharger (two-stage turbocharger), since here different requirements and peripheral conditions exist. For example, care must be taken in a two-stage turbocharger that the hot exhaust gas flow during passage through from the high pressure stage to the low pressure stage occurs without all too great a drop in the exhaust gas temperature or, as the case may be, the flow velocity. In addition a direction of flow must be maintained, that means, that the exhaust gas spiral must exhibit a prescribed predetermined shape.
For this reason, at this time no commercially available two-stage turbochargers are known, in which the two turbocharger stages are integrated into a single common housing.